Polymers functionalized with ion-specific recognition elements

ABSTRACT

Polymeric compounds containing polymer backbones functionalized with ion-specific recognition elements and methods for the use of these compounds are described herein. The polymeric compounds may contain multiple types of ion-specific recognition elements depending on a specific application. The polymeric compounds can be used to remove ionic species from a solution, for example, in separations applications in which a single or multiple types of ionic species are desired to be removed from the solution.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.12/623,943, filed Nov. 23, 2009, which claims priority to U.S.Provisional Application No. 61/118,170, filed Nov. 26, 2008, which areincorporated herein by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with government support under Grant NumberGM-58907 awarded by the National Institutes of Health Grant and GrantNumber CHE-0645563 awarded by the National Science Foundation. Thegovernment has certain rights in this invention.

BACKGROUND

The selective separation of alkaline salts and ionic species fromaqueous media is useful in various chemical, biological, medical, andindustrial applications. For example selective separation techniques canbe used in the production of commodity materials (e.g., bromine,potassium, etc.) from high salt sources, such as the Dead Sea and theGreat Salt Lake. Selective separation is also used in biologicalprocesses such as the regulation of taste and the maintenance of osmoticbalance in cells. Such separations also can be useful in medicalapplications, for example, the removal of ions from blood or reducingthe uptake of ions from ingested foods. Removing or controlling ionlevels in a subject can be useful in the control or treatment ofnumerous disease conditions including hyperkalemia andhyperphosphatemia, which are often associated with diabetes or renalfailure.

SUMMARY

Polymeric compounds useful in binding ionic species and methods fortheir use are provided. The polymeric compounds include a polymerbackbone that is functionalized with ion-specific recognition elements.The polymer backbone of the polymeric compounds may be functionalizedwith multiple types of ion-specific recognition elements. The polymericcompounds can be used in methods to remove ionic species from asolution. Additionally, methods to treat or prevent an ion imbalance ina subject including the steps of selecting a subject with or suspectedof having an ion imbalance and administering to the subject a polymericcompound as described herein.

The details of one or more examples of the polymeric compounds andmethods are set forth in the accompanying drawings, figures, and thedescription below. Other features, objects, and advantages will beapparent from the description, drawings, and figures, and from theclaims.

DESCRIPTION OF FIGURES

FIG. 1 shows overlaid ¹H NMR spectra of CD₂Cl₂ solutions of (a)octamethylcalix[4]pyrrole (29 mM) and (b) PMMA (125 mM, based on therepeat unit) after 1) adding 0.5 mL of a D20 solution of TBAF (90 mM),ii) shaking the tube vigorously, and iii) allowing the phases toseparate, (c) a calix[4]pyrrole functionalized PMMA homopolymer(effective concentration of the calix[4]pyrrole repeat unit=6.5 mM), (d)a solution of the homopolymer after being subjected to the sametreatment applied in the case of (a) and (b) (* indicates residualsolvent).

FIG. 2 shows overlaid ¹H NMR spectra of CD₂Cl₂ solutions of (a) amixture of octamethylcalix[4]pyrrole (29 mM) and (b) PMMA (125 mM basedon the repeat unit) after i) adding 0.5 mL of a D20 solution of TBACl(108 mM), ii) shaking the tube vigorously, and iii) allowing the phasesto separate, (c) a calix[4]pyrrole functionalized co-polymer (effectiveconcentration of the calix[4]pyrrole repeat unit=6.5 mM), and (d) asolution of the co-polymer after being subjected to the same treatmentapplied in the case of (a) and (b) (* indicates residual solvent).

FIG. 3 shows aqueous solutions of a dye with a chloride anion (toplayers) after treatment with: a) CH₂Cl₂ (bottom layer); b) a CH₂Cl₂solution of octamethylcalix[4]pyrrole (bottom layer); c) a CH₂Cl₂solution of benzo-15-crown-5 ether (bottom layer); d) a CH₂Cl₂ solutionof the calix[4]pyrrole and the crown ether (bottom layer); and e) aCH₂Cl₂ solution of Copolymer I (bottom layer).

FIG. 4 shows UV-vis spectra of aqueous solutions of a dye with achloride anion (initial concentration=25.5 nM) after exposing to anequal volume of a CH2Ch solution of Copolymer I (effective concentrationof the calix[4]pyrrole and crown ether repeat units=1.56 and 1.22 mM),octamethylcalix[4]pyrrole (1.56 mM), benzo-15-crown-5 ether (1.22 mM),or a mixture of the calix[4]pyrrole and the crown ether (1.56 and 1.22mM).

FIG. 5 shows UV-vis spectra of aqueous solutions of a dye with apotassium cation (initial concentration=216.86 nM) after exposing to anequal volume of a CH₂Cl₂ solution of Copolymer I (effectiveconcentration of the calix[4]pyrrole and crown ether repeat units=1.56and 1.22 mM), octamethylcalix[4]pyrrole (1.56 mM), benzo-15-crown-5ether (1.22 mM), or a mixture of the calix[4]pyrrole and the crown ether(1.56 and 1.22 mM).

FIG. 6 shows ¹⁹F NMR spectra of CD₂Cl₂ solutions of Copolymer I(effective [calix[4]pyrrole]=6.25 mM), Copolymer II([calix[4]pyrrole]=6.50 mM), and Copolymer III (no calix[4]pyrrole)after adding D20 solutions of KF (3.4 M).

DETAILED DESCRIPTION

Polymeric compounds including a polymer backbone that is functionalizedwith ion-specific recognition elements and methods for their use aredescribed herein. The polymer backbone of a polymeric compound asdescribed herein may be functionalized with multiple types ofion-specific recognition elements. The multiple types of ion-specificelement may include elements capable of recognizing and/or bindingseparately or jointly both anionic and/or cationic species. Anion-specific element capable of jointly recognizing anionic and cationicspecies could recognize separate anionic and cationic molecules or azwitterionic molecule, i.e., a molecule containing both positively andnegatively charges components. Such polymeric compounds can be used toremove ionic species from a solution, for example, in separationsapplications in which a single or multiple types of ionic species aredesired to be removed from a solution (e.g., an aqueous solution).

Ion-specific recognition elements useful with the polymeric compoundsdescribed herein include anionic, cationic, and zwitterionic recognitionelements. Mixtures of two or more types of ion-specific recognitionelements, i.e., anionic, cationic, or zwitterionic, can be used with thepolymeric compounds described herein. The term ion-specific recognitionelement is used herein to indicate a functional element that is capableof binding to or otherwise interacting with (e.g., complexation) anionic species. Examples of ion-specific recognition elements includecalixpyrroles, crown ethers, calixarenes, cryptands, polyaaza,macrocycles, expanded porphyrins, pyrroleamides, indoleamides,substituted ureas, polyamides, and derivatives thereof. Mixtures ofion-specific recognition elements, e.g., a mixture of calixpyrroles andcrown ethers, can be used in the same polymeric compound. An example ofa calixpyrrole is octamethylcalix[4]pyrrole, which is known to bindhalide ions in a 1:1 ratio and has the following structure:

The methyl groups of the octamethylcalix[4]pyrrole can be replaced withsubstitutions of various constituents including alkyl, alkenyl, alkynl,heteroalkyl, heteroalkenyl, heteroalkenyl, cycloalkyl, cycloalkenyl,cycloalkynl, cycloheteroalkyl, cycloheteroalkenyl, cycloheteroalkenyl,or aryl groups. Examples of possible substitutions for a methyl group ofoctamethylcalix[4]pyrrole include:

and —CH2OH. An example of a crown ether is a benzo-15-crown-5 ether,which is known to from 2:1 sandwich complexes with potassium cations andhas the following structure:

The benzene ring (or other carbon atoms) of the benzo-15-crown-5 ethercan be substituted with various constituents including alkyl, alkenyl,alkynl, heteroalkyl, heteroalkenyl, heteroalkenyl, cycloalkyl,cycloalkenyl, cycloalkynl, cycloheteroalkyl, cycloheteroalkenyl,cycloheteroalkenyl, or aryl groups. An example of a substitution groupto the benzene ring of a benzo-15-crown-5 ether includes:

Polymer backbones useful with the polymeric compounds described hereininclude polymers capable of being functionalized with the ion-specificrecognition elements described herein. Examples of polymer backbonessuitable for use with the polymeric compounds described herein includehomopolymer backbones and co-polymer backbones. The term homopolymerbackbone is used herein to indicate a polymer backbone with a singletype of repeat unit, e.g., polymethyl methacrylate, polyacryonitrile,polyacrylate, polystyrene, polyester, polyurethane, or polyamide.Polymethyl methacrylate has the following structure:

The term co-polymer backbone is used herein to indicate a polymerbackbone with multiple (e.g., two or more) types of repeat units, e.g.,ABS plastic, SBR, Nitrile rubber, styrene-acrylonitrile,styrene-isoprene-styrene (SIS) and ethylene-vinyl acetate. The multipletypes of repeat units can repeat in various patterns, e.g., alternating,periodic, random, block, or with various tacticities, e.g.,syndiotactic, isotactic, or random, and be useful with the polymericcompounds as described herein. Various other types of homopolymers andco-polymers useful with the polymeric compounds described herein will beapparent to those of skill in the polymer arts.

Polymeric compounds as described herein include homopolymers andco-polymers. When used in reference to the polymeric compounds describedherein, the term homopolymer indicates a polymer that has a uniformlyfunctionalized backbone monomer, e.g., a poly(octamethylcalix[4]pyrrolefunctionalized methyl methacrylate), which has the following structure:

When used in reference to the polymeric compounds described herein, theterm co-polymer indicates a polymer that has functionalized backbonemonomers that may be spaced apart from each other or multiple, differingfunctionalized backbone monomers that may be spaced apart from eachother. An example of a polymer that has functionalized backbone monomersthat may be spaced apart from each other is a polymer with a partiallyoctamethylcalix[4]pyrrole functionalized polymethyl methacrylatebackbone, e.g., a compound with the following structure:

An example of a polymer that has multiple, differing functionalizedbackbone monomers that may be spaced apart from each other is a multiple(e.g., octamethylcalix[4]pyrrole and benzo-15-crown-5) functionalizedpolymethyl methacrylate backbone, e.g., a compound with the followingstructure:

The polymer backbone of the polymeric compounds as described herein canbe a homopolymer, as shown by the polymethyl methacrylate backbones usedabove to illustrate the homopolymer and co-polymer versions of thepolymeric compounds as described herein, or, as indicated above, thebackbone of the polymeric compounds can be a co-polymer and have ahomopolymer or co-polymer type distribution of functional moieties.

The ion-specific recognition elements useful with the polymericcompounds described herein are covalently linked to the polymerbackbone. The covalent linkage can be a direct connection to a backboneside chain, e.g., the polymethyl methacrylate side chain, or the linkagecan be made through a linker molecule. Linker molecules can themselvesbe substituted or unsubstituted and include, for example, alkyl,alkenyl, alkynl, heteroalkyl, heteroalkenyl, heteroalkenyl, cycloalkyl,cycloalkenyl, cycloalkynl, cycloheteroalkyl, cycloheteroalkenyl,cycloheteroalkenyl, and aryl groups.

The polymeric compounds described herein can be prepared in a variety ofways known to one skilled in the art of organic synthesis or variationsthereon as appreciated by those skilled in the art. The polymericcompounds described herein can be prepared from readily availablestarting materials. Optimum reaction conditions may vary with theparticular reactants or solvents used, but such conditions can bedetermined by one skilled in the art.

Variations on the polymeric compounds described herein include theaddition, subtraction, or movement of the various constituents asdescribed for each compound, as well as modification of the polymercompound's tacticity. Additionally, compound synthesis can involve theprotection and deprotection of various chemical groups. The use ofprotection and deprotection, and the selection of appropriate protectinggroups can be determined by one skilled in the art. The chemistry ofprotecting groups can be found, for example, in Greene, et al.,Protective Groups in Organic Synthesis, 2d. Ed., Wiley & Sons, 1991,which is incorporated herein by reference in its entirety.

As used herein, the terms alkyl, alkenyl, and alkynyl includesubstituted and unsubstituted straight- and branched-chain monovalentsubstituents. Examples include methyl, ethyl, isobutyl, 3-butynyl, andthe like. Heteroalkyl, heteroalkenyl, and heteroalkynyl are similarlydefined but may contain O, S, or N heteroatoms or combinations thereofwithin the backbone. Cyclo versions of alkyl, alkenyl, alkynyl,heteroalkyl, heteroalkenyl, and heteroalkynyl molecules contain a cycliccore, but are similarly defined otherwise and may include varioussubstitutions. The term substituted indicates the main substituent hasattached to it one or more additional components, such as, for example,OH, halogen, or one of the substituents listed above.

Reactions to produce the compounds described herein can be carried outin solvents, which can be selected by one of skill in the art of organicsynthesis. Solvents can be substantially nonreactive with the startingmaterials (reactants), the intermediates, or products under theconditions at which the reactions are carried out, i.e., temperature andpressure. Reactions can be carried out in one solvent or a mixture ofmore than one solvent. Product or intermediate formation can bemonitored according to any suitable method known in the art. Forexample, product formation can be monitored by spectroscopic means, suchas nuclear magnetic resonance spectroscopy (e.g., ¹H or ¹³C) infraredspectroscopy, spectrophotometry (e.g., UV-visible), or massspectrometry, or by chromatography such as high performance liquidchromatography (HPLC) or thin layer chromatography.

The methods described herein include a method of using the polymericcompounds described above to remove ionic species from a solution. Ionicspecies that the polymeric compounds described herein are able to removeinclude cationic species (such as sodium and potassium and their counterions), anionic species (such as fluoride, chloride, bromide, and iodineand their counter ions), and zwitterionic species and salts and mixturesthereof. Examples of applications of the methods of using the polymericcompounds described herein may include corrosion prevention (e.g.,chloride, carbonate, and sulfate control under conditions ofcombustion), waste remediation (e.g., sulfate extraction from tankwaste), toxin control (e.g., mitigating the effects of overexposure tocyanide or fluoride), and health care (i.e., enhanced phosphate anion orpotassium cation removal under conditions of hemodialysis or throughingestion by a subject of the polymeric compounds described herein tohelp reduce elevated ion levels (e.g., phosphate imbalance disorder).Methods of treating or preventing an ion imbalance in a subject includeselecting a subject with or suspected of having an ion imbalance andadministering to the subject a polymeric compound as described herein.As used herein treating means providing a therapeutic or prophylacticbenefit to the subject, e.g., eradicating, reducing, ameliorating, orpreventing an indicated disease or symptom.

The polymeric compounds described herein can be provided in apharmaceutical composition for administering to a subject. Depending onthe intended mode of administration, the pharmaceutical composition canbe in the form of solid, semi-solid or liquid dosage forms, such as, forexample, tablets, suppositories, pills, capsules, powders, liquids, orsuspensions, preferably in unit dosage form suitable for singleadministration of a precise dosage. The compositions will include aneffective amount of the compounds described herein in combination with apharmaceutically acceptable carrier and, in addition, may include othermedicinal agents, pharmaceutical agents, carriers, or diluents. Bypharmaceutically acceptable is meant a material that is not biologicallyor otherwise undesirable, which can be administered to an individualalong with the selected substrate without causing significantundesirable biological effects or interacting in a deleterious mannerwith any of the other components of the pharmaceutical composition inwhich it is contained.

As used herein, the term carrier encompasses any excipient, diluent,filler, salt, buffer, stabilizer, solubilizer, lipid, stabilizer, orother material well known in the art for use in pharmaceuticalformulations. The choice of a carrier for use in a composition willdepend upon the intended route of administration for the composition.The preparation of pharmaceutically acceptable carriers and formulationscontaining these materials is described in, e.g., Remington'sPharmaceutical Sciences, 21st Edition, ed. University of the Sciences inPhiladelphia, Lippincott, Williams & Wilkins, Philadelphia Pa., 2005.Examples of physiologically acceptable carriers include buffers such asphosphate buffers, citrate buffer, and buffers with other organic acids;antioxidants including ascorbic acid; low molecular weight (less thanabout 10 residues) polypeptides; proteins, such as serum albumin,gelatin, or immunoglobulins; hydrophilic polymers such aspolyvinylpyrrolidone; amino acids such as glycine, glutamine,asparagine, arginine or lysine; monosaccharides, disaccharides, andother carbohydrates including glucose, mannose, or dextrins; chelatingagents such as EDTA; sugar alcohols such as mannitol or sorbitol;salt-forming counterions such as sodium; and/or nonionic surfactantssuch as TWEEN™ (ICI, Inc.; Bridgewater, N.J.), polyethylene glycol(PEG), and PLURONICS™ (BASF; Florham Park, N.J.). A furtherconsideration in choosing a carrier is the function of the polymericcomposition to be carried, e.g., if a polymeric compound as describedherein has anionic ion-recognition elements, a carrier that does notcontain anions that would be recognized can be chosen.

Compositions containing the polymeric compounds described hereinsuitable for parenteral injection may comprise physiologicallyacceptable sterile aqueous or nonaqueous solutions, dispersions,suspensions or emulsions, and sterile powders for reconstitution intosterile injectable solutions or dispersions. Examples of suitableaqueous and nonaqueous carriers, diluents, solvents or vehicles includewater, ethanol, polyols (propyleneglycol, polyethyleneglycol, glycerol,and the like), suitable mixtures thereof, vegetable oils (such as oliveoil) and injectable organic esters such as ethyl oleate. Proper fluiditycan be maintained, for example, by the use of a coating such aslecithin, by the maintenance of the required particle size in the caseof dispersions and by the use of surfactants.

These compositions may also contain adjuvants such as preserving,wetting, emulsifying, and dispensing agents. Prevention of the action ofmicroorganisms can be ensured by various antibacterial and antifungalagents, for example, parabens, chlorobutanol, phenol, sorbic acid, andthe like. It may also be desirable to include isotonic agents, forexample, sugars, sodium chloride, and the like. Prolonged absorption ofthe injectable pharmaceutical form can be brought about by the use ofagents delaying absorption, for example, aluminum monostearate andgelatin.

Solid dosage forms for oral administration of the compounds describedherein include capsules, tablets, pills, powders, and granules. In suchsolid dosage forms, the polymeric compound described herein is admixedwith at least one inert customary excipient (or carrier) such as sodiumcitrate or dicalcium phosphate or (a) fillers or extenders, as forexample, starches, lactose, sucrose, glucose, mannitol, and silicicacid, (b) binders, as for example, carboxymethylcellulose, alignates,gelatin, polyvinylpyrrolidone, sucrose, and acacia, (c) humectants, asfor example, glycerol, (d) disintegrating agents, as for example,agar-agar, calcium carbonate, potato or tapioca starch, alginic acid,certain complex silicates, and sodium carbonate, (e) solution retarders,as for example, paraffin, (f) absorption accelerators, as for example,quaternary ammonium compounds, (g) wetting agents, as for example, cetylalcohol, and glycerol monostearate, (h) adsorbents, as for example,kaolin and bentonite, and (i) lubricants, as for example, talc, calciumstearate, magnesium stearate, solid polyethylene glycols, sodium laurylsulfate, or mixtures thereof. In the case of capsules, tablets, andpills, the dosage forms may also comprise buffering agents.

Solid compositions of a similar type may also be employed as fillers insoft and hard-filled gelatin capsules using such excipients as lactoseor milk sugar as well as high molecular weight polyethyleneglycols, andthe like.

Solid dosage forms such as tablets, dragees, capsules, pills, andgranules can be prepared with coatings and shells, such as entericcoatings and others well known in the art. They may contain opacifyingagents, and can also be of such composition that they release thepolymeric compound or compounds in a certain part of the intestinaltract in a delayed manner. Examples of embedding compositions which canbe used are polymeric substances and waxes. The polymeric compounds canalso be in micro-encapsulated form, if appropriate, with one or more ofthe above-mentioned excipients.

Liquid dosage forms for oral administration of the polymeric compoundsdescribed herein include pharmaceutically acceptable emulsions,solutions, suspensions, syrups, and elixirs. In addition to thepolymeric compounds, the liquid dosage forms may contain inert diluentscommonly used in the art, such as water or other solvents, solubilizingagents, and emulsifiers, as for example, ethyl alcohol, isopropylalcohol, ethyl carbonate, ethyl acetate, benzyl alcohol, benzyl alcohol,benzyl benzoate, propyleneglycol, 1,3-butyleneglycol, dimethylformamide,oils, in particular, cottonseed oil, groundnut oil, com germ oil, oliveoil, castor oil, sesame oil, glycerol, tetrahydrofurfuryl alcohol,polyethyleneglycols, and fatty acid esters of sorbitan, or mixtures ofthese substances, and the like.

Besides such inert diluents, the composition can also include adjuvants,such as wetting, emulsifying, suspending, sweetening, flavoring, orperfuming agents.

Suspensions, in addition to the polymeric compounds, may containsuspending agents, as for example, ethoxylated isostearyl alcohols,polyoxyethylene sorbitol and sorbitan esters, microcrystallinecellulose, aluminum metahydroxide, bentonite, agar-agar and tragacanth,or mixtures of these substances, and the like.

The examples below are intended to further illustrate certain aspects ofthe methods and compounds described herein, and are not intended tolimit the scope of the claims.

EXAMPLES Example 1 Preparation of Calix[4]Pyrrole Functionalized PMMAHomopolymer and Co-Polymer

Calix[4]pyrrole Functionalized PMMA Homopolymer

A N-methylmethacrylamide functionalized calix[4]pyrrole monomer wasprepared in 82% yield from a hydroxylmethyl calixpyrrole derivativethrough treatment with methacryloyl chloride under basic conditions. TheN-methylmethacrylamide functionalized calix[4]pyrrole monomer provedamenable to polymerization using conventional free radical methods. SeeG. Odian, Principles of Polymerization, 4th Ed., John Wiley and Sons,Inc., 2004, Chapter 3. A homopolymer was prepared by dissolving theN-methylmethacrylamide functionalized calix[4]pyrrole monomer in THF(0.3 M) followed by treatment with 1 mol % of azoisobutyronitrile(AIBN). After stirring at 70° C. for 17 h under an atmosphere ofnitrogen, the resulting viscous solution was added dropwise into excessmethanol with rapid stirring. This caused precipitation of thehomopolymer, which was later isolated via filtration in 66% yield. Usinggel permeation chromatography (GPC), the polymer was found to have anumber-average molecular weight (Mn) of 23,600 Da (relative to PMMAstandards) and a polydispersity index (POI) of 2.3.

Calixf 4]pyrrole Functionalized PMMA Co-Polymer

A copolymer of N-methylmethacrylamide functionalized calix[4]pyrrole andmethyl methacrylate (MMA) was prepared using the conventional freeradical polymerization protocol described above. The reaction produced a77% yield of the copolymer from a 1:10 mixture of N-methylmethacrylamidefunctionalized calix[4]pyrrole monomer and MMA. Using GPC, the copolymerwas found to possess a Mn of 85,500 Da and a PDI of 2.1. The co-polymerwas highly soluble in most common organic solvents, includingdichloromethane.

¹H NMR spectroscopic analysis (CD₂Cl₂) of the co-polymer indicated thatthere were approximately fourteen methacrylate units per calixpyrroleunit within the co-polymer. For comparison, a sample of PMMA (Mn=40,700;PDI=1.5) was prepared using a procedure analogous to that used to obtainthe homopolymer and copolymer. Thermal analysis of the co-polymerrevealed a decomposition temperature (Ta) at 272° C., which isintermediate between the respective T_(dS) found for the homopolymer(270° C.) and the PMMA homopolymer (276° C.) used for comparison.

These results indicate that the physical properties of co-polymersprepared from MMA and various methacrylate monomers functionalized withion-specific recognition elements may be tuned through the selection ofspecific functionalized monomers.

Example 2 Binding Ions Under Interfacial Conditions Using the Co-Polymerof Example 1

The ability of the co-polymer to bind anions under interfacialconditions was explored. As shown in FIG. 1, addition of a D20 solutionof tetrabutylammonium fluoride (TBAF, 90 mM) to a CD₂Cl₂ solution of theco-polymer (effective concentration of the calix[4]pyrrole repeatunit=6.5 mM) resulted in a substantial downfield shift in the pyrrole NHprotons (as typically seen upon anion binding). Further, peaksascribable to the methylene units in the TBA⁺ counter cation (at δ=3.2ppm) were seen, indicating that both the anion (F⁻) and the cation werepresent in the organic phase. In contrast, no shifts in the NHresonances and no TBA⁺-ascribable peaks were observed when a 29 mMsolution of octamethylcalix[4]pyrrole in CD₂Cl₂ was exposed to aqueoussolutions of TBAF. Likewise, no evidence of uptake of TBA into theorganic phase (absence of any discernible peak at δ=3.2 ppm) was seenwhen analogous experiments were repeated with the MMA homopolymer.

The ability of the co-polymer to extract several other TBA salts wasalso examined. While no extraction was seen in the case of aqueoussolutions of tetrabutylammonium dihydrogen phosphate, upon addition ofTBACI downfield shifts in the NH proton signals were seen to be greaterthan those observed with TBAF for analogous anion concentrations (seeFIG. 2). Such results, which are consistent with an enhanced ability toextract chloride relative to fluoride or dihydrogen phosphate, runcounter to the relative anion affinities seen in dichloromethane.However, they are in accord with what one would expect based on theso-called Hofineister bias (see R. Custelcean and B. A. Moyer, Eur. J.Inorg. Chem. 2007, 1321-1340; F. Hofmeister, Arch. Exp. Pathol.Pharmakol. 1888, 24, 247-260), namely that a more hydrophobic anion,such as chloride (ΔG_(h)=−340 kJ moL⁻¹), is extracted more easily than ahighly hydrophilic species, such as dihydrogen phosphate (ΔG_(h)=−465 kJmoL⁻¹), or fluoride (ΔG_(h)=−465 kJ moL⁻¹). See Table 1.1 of B. A. Moyerand P. V. Bonnensen, Physical Factors in Anion Separations, inSupramolecular Chemistry of Anions, A. Bianchi, K. Bowman-James, and E.Garcia-España, Eds., Wiley-VCH, New York, 1997. Consistent with thisrationale is the finding that both the control MMA homopolymer andcalixpyrrole were able to extract TBACl under the aforementionedinterfacial conditions, albeit with efficiencies of less than 35%relative to the co-polymer (as calculated from NMR integrations of theMMA methyl ester, P-pyrrolic, and TBA⁺ signals, as appropriate). On theother hand, that efficient extraction of TBAF was only seen in the caseof the co-polymer (and not the PMMA control or free calixpyrrole)underscores the notion that the calixpyrrole receptor appended to thePMMA backbone is playing a role in overcoming the Hofineister biasassociated with this highly hydrophilic species.

Further support that the co-polymer could bind fluoride and chlorideanions came from thermal analyses. Specifically, after independentlyexposing TBAF or TBACI to the co-polymer as described above, thesesamples as well as PMMA controls were subjected to thermogravimetricanalysis. For the sample of the co-polymer exposed to TBAF, a 10% massloss was observed upon heating to 230° C., a temperature just below theT_(d) of the copolymer (262° C.). This compares well with thetheoretical mass loss of 11.5% assuming the TBAF became completelyvolatilized over the aforementioned temperature range and was present ina 1:1 stoichiometry relative to each calix[4]pyrrole unit in the polymerchain. In contrast, the sample of the co-polymer exposed to TBAClexhibited a 19% mass loss (theoretical: 12.1%) upon heating to 230° C.Considering the relative extraction abilities of the co-polymer towardsTBACl and TBAF (see above), the observed mass loss was consideredreasonable. For comparison, the PMMA controls lost ≦2% of their massesprior to polymer decomposition (277° C.), which leads to the conclusionthat only minimal amounts TBAF or TBACl were present in these samplesafter extraction.

Example 3 Preparation of Calix[4]pyrrole and benzo-15-crown-5 etherFunctionalized PMMA Co-Polymers

All solvents were dried before use according to standard literatureprocedures. Unless specifically indicated, all other chemicals andreagents used in this study were purchased from commercial sources andused as received. ¹H, ¹³C and ¹⁹F NMR spectra used in thecharacterization of products and quantification of extracted KF wererecorded on Varian Unity 300 or 400 MHz and Bruker 250 MHz AC-3000spectrometers using a residual protio solvent as the reference.Low-resolution FAB and CI mass spectra were obtained on a Finningan MATTSQ 70 mass spectrometer (Finningan MAT; San Jose, Calif.). Highresolution FAB and CI mass spectra were obtained on a VG ZAB2-E massspectrometer (Kevex/Fisons Instruments; San Carlos, Calif.). GPCanalyses were performed using a Waters HPLC system consisting of HR-1,HR-3, and HR-SE STYRAGEL™ columns arranged in series, a 1515 pump, and a2414 RI detector; reported molecular weights are relative to polystyrenestandards in DMF (0.01 M LiBr) at 40° C. (column temperature) (WatersCorporation; Milford, Mass.). Thermogravimetric analyses were performedusing a Mettler Toledo TGA/SDTA851 e equipped with a TS0801RO sampleautomated loader (Mettler Toledo; Columbus, Ohio). A Varian SpectrAA-40Atomic Absorption Spectrometer was used in flame emission mode with anacetylene/air (18:2) mixture to quantify the extracted potassium salts;the samples for these measurements were diluted with ethyl acetate priorto recording the emission intensities at 766.5 nm (Varian, Inc.; PaloAlto, Calif.). UV-vis analyses were performed with a Chebios Optimum-OneUV-vis spectrophotometer (Chebios s.r.1.; Rome, Italy).

Synthesis

Three co-polymers were prepared based on the following formula:

Specifically Copolymer I (x=1.0, y=14, z=0.8; M_(n)=57 kDa), CopolymerII (x=1.0, y=14, z=0; M_(n)=90 kDa), and Copolymer III (x=0, y=12,z=1.0; M_(n)=90 kDa) were prepared from MMA, calix[4)pyrrole, and aN-methylmethacrylamide benzo-15-crown-5 derivative using conventionalfree radical polymerization techniques as described above. (Copolymer IIwas prepared as above for Example 1.)

Copolymer I

Copolymer I was prepared by dissolving calix[4]pyrrole monomer,N-methylmethacrylamide benzo-15-crown-5 derivative monomer, and MMA in1:1:10 ratio in THF (total conc.: approx. 0.3 M) followed by treatmentwith 1 mol % of azoisobutyronitrile (AIBN). After stirring at 70° C. for17 h under an atmosphere of nitrogen, the resulting viscous solution wasadded dropwise to excess methanol. This caused precipitation ofCopolymer I, which was subsequently isolated via filtration in 79% yieldas a white solid. ¹H NMR (500 MHz, CD₂Cl₂) δ: 0.82 and 0.89 (brsinglets, 59.56H, PMMA CH3), 1.51 (br s, 21H, calixpyrrole meso-CH3),1.82 (br m, 48.25H, PMMA CH2), 3.57 (br s, 68H, PMMA OCH₃), 3.68 (br m,7.5H, crown ether CH2), 3.84 (br s, 3.75H, crown ether CH2), 4.08 (br s,6H, crown ether CH2 and calixpyrrole meso-CH2), 5.89 (b, 8H, pyrroleCH), 6.83-7.26 (6H, NH and crown ether aromatic protons). GPC: Mn: 50.2kDa, PDI: 2.1.

Copolymer III

Using conditions analogous to those used to prepare Copolymer I, a 76%yield of Copolymer III was obtained as a yellow solid from a 1:10mixture of N-methylmethacrylamide benzo-15-crown-5 derivative monomerand MMA. ¹H NMR (500 MHz, CD₂Cl₂) δ: 0.81 (br s, 16.86H, polymerbackbone CH3), 0.81 (br s, 10.30H, polymer backbone CH3), 1.80 (br m,19.12H, polymer backbone CH2), 3.58 and 3.68 (s and s, 32.96H polymerbackbone CH3 and crown ether CH2), 3.84 (br s, 2H, crown ether CH2),4.07 (br s, 2H, crown ether CH2), 6.81-7.26 (3H, crown ether aromaticprotons). GPC: Mn: 33.2 kDa, PDI: 2.1.

Example 4 Copolymer I can Extract Water Soluble Dyes with Chloride andPotassium Counterions

Chloride

Initial qualitative evidence that Copolymer I, which contains bothcalix[4]pyrrole and crown ether subunits, could extract chloride saltsinto organic media came from a visual test involving a water soluble dyethat contains a chloride counteranion, specifically:

Extraction was performed by adding 3 mL of an organic solution to 3 mLof an aqueous solution containing the dye with vigorous shaking thenallowing the organic and aqueous phases to separate. Treatment of anaqueous solution of the dye (25.5 μM) with a CH₂Cl₂ solution ofCopolymer I (effective concentration of the calix[4]pyrrole and crownether repeat units=1.56 and 1.22 mM, respectively) resulted in a coloredorganic (lower) phase (see FIG. 3 e). As controls, solutions of the dyeswere also exposed to a CH₂Cl₂ solution (see FIG. 3 a), a CH₂Cl₂ solutionof free calix[4]pyrrole (1.56 mM) (see FIG. 3 b), a CH₂Cl₂ solution offree benzo-15-crown-5 (1.22 mM) (see FIG. 3 c), and a mixture of freecalix[4]pyrrole and free benzo-15-crown-5 in CH₂Cl₂ (1.56 and 1.22 mM,respectively) (see FIG. 3 d), however no transfer of color was observedfrom the upper aqueous phase to the lower organic phase. These resultswere quantified using UV-vis spectroscopy (1 mL aliquots of thesolutions were diluted to 10 mL with water then analyzed). As shown inFIG. 4, analysis of the water phases of these extraction experimentsconfirmed that Copolymer I was able to extract the dye into the organicphase more effectively (>54%) than free calix[4]pyrrole, freebenzo-15-crown-5, or their mixture.

Potassium

Similar qualitative and quantitative results were observed when aqueoussolutions of a water soluble dye that contains a potassium counteractionwas examined. The dye had the following structure:

In this case, Copolymer I proved more effective as an extractant (>30%)relative to free calix[4]pyrrole, free benzo-15-crown-5, or theirmixtures (as used above) (see UV-vis spectroscopy results in FIG. 5).

Example 5 Copolymer I can Extract Potassium Fluoride

Whether Copolymer I could extract a salt consisting of two hard ions,namely potassium fluoride was examined using ¹⁹F NMR. In parallel, theextraction properties of Copolymer II and Copolymer III were examined toassess the relative importance of each individual ion recognition uniton the overall extraction properties of Copolymer I. To prepare thesamples, a D20 solution of KF (0.5 mL, 3.4 M) was added to a 0.75 mLsample of a CD₂Cl₂ solution of the individual polymer underinvestigation (i.e., Copolymer I, Copolymer II, or Copolymer III,respectively, as well as various controls). To each sample, 1 μL (14.21mM) of fluorobenzene was added as an internal ¹⁹F NMR standard. Aftershaking the tubes vigorously, the phases were separated by subjectingthem to centrifugation for 10 min. The CD₂Cl₂ layer obtained from eachtube was then recorded using ¹⁹F NMR spectroscopy and the amount of KFwas quantified via peak integration relative to the internalfluorobenzene standard. Following this procedure, the error in fluorideanion concentration measured in the extraction experiments described inthe text was estimated to be less than 0.03 mM. As shown in FIG. 6,addition of a 3.4 M D20 solution of KF to a CD₂Cl₂ solution of CopolymerI (effective concentration of the calix[4]pyrrole and crown ether repeatunits=6.25 and 4.86 mM, respectively) resulted in the appearance of asignal at δ=−121.7 ppm in the ¹⁹F NMR spectrum of the organic phase (thetubes were shaken vigorously, and then the phases were separated withthe aid of centrifugation (10 min)) A similar signal, but of reducedintensity, was seen in the case of Copolymer II, whereas very littlesignal was observed in the case of Copolymer III.

To quantify the amount of fluorine present in the organic phases of theKF extraction experiments, fluorobenzene (final concentration: 14.21 mM)was added to each sample as an internal standard (δ=−114.3 ppm). Basedon comparative integrations (i.e., comparing total fluoride content inthe CD₂Cl₂ layer relative to this standard), Copolymer I was found to becapable of extracting KF more efficiently (7.55±0.04 mM) then CopolymerII (5.71±0.03 mM) under conditions where the effective concentration ofthe calix[4]pyrrole repeat units in both polymers were essentially thesame (6.25 mM versus 6.50 mM for Copolymer I and Copolymer II,respectively). In addition, both Copolymer I and Copolymer II were foundto extract more fluoride into the organic phase than Copolymer III([F]=0.34±0.03 mM in the CD2Ch layer), which that does not contain anycalix[4]pyrrole subunits, as noted above. As control experiments,extractions were also performed in an analogous manner using freecalix[4]pyrrole, free benzo-15-crown-5, MMA homopolymer, an equimolarmixture of free calix[4]pyrrole and free benzo-15-crown-5, and acalyx[4]pyrrole-benzo-15-crown-5 pseudo dimer, which was envisioned as asmall molecule analogue of Copolymer I. No quantifiable fluorine signalwas observed in the organic phase when any of these control systems wereused as extractants.

Flame emission spectroscopy (FES) was used to confirm the co-extractionof potassium in the above experiments (see K. W. Jackson, S. J. Lu,Anal. Chem. 1998, 70, 363). A calibration curve was generated using astandard solution of potassium tetrakis(2-thienyl)borate (PTTB) in ethylacetate/methylene chloride (9/1 v/v). The error in potassiumconcentrations measured following the extraction experiments isestimated to be less than 0.05 mM. The organic phase obtained afterextracting KF with Copolymer I afforded an emission intensity (El) of0.401 (at 766.5 nm, i.e., the emission wavelength of the excitedpotassium ion produced by the flame source) after dilution with a knownamount of ethyl acetate. By way of comparison, the organic phasesproduced EI values of 0.277 and 0.038, respectively when Copolymers IIand III were used as extractants under otherwise identical conditions.Extracted potassium concentrations of 6.84, 4.73, and 0.65±0.05 mM werecalculated for CD₂Cl₂ solutions of Copolymers I, II, and III (ateffective crown ether concentrations of 5.60, 0.00, and 5.00 mM). Thesevalues agree with those obtained from the ¹⁹F NMR data. A summary of theKF extraction data is presented in Table 1.

TABLE 1 Summary of KF extraction efficiencies.^(a) eff. (%) eff. (%)eff. (%) eff. (%) Compound calix:crown^(c) (total)^(d,e) (calix)^(d,f)(total)^(e,g) (crown)^(g,h) Copolymer I 1.0:0.8 67 121 61 137 CopolymerII 1.0:0.0 88 88 73 ^(i) Copolymer III 0.0:1.0 6 ^(i) 12 12 Pseudodimer^(b) 1.0:1.0 0 0 0 0 ^(a)Extraction efficiencies (eff.) arereported as the percent (%) of extractant populated with KF uponexposure to a saturated aqueous solution of KF.^(b)calix[4]pyrrole-benzo-15-crown-5 pseudo dimer ^(c)Relative molarratios of calixpyrrole (calix) to crown ether (crown) units in theextractant. ^(d)Calculated from total fluoride extracted. ^(e)Based onthe total number of ion receptors (calixpyrrole plus crown ether) in theextractant. ^(f)Based on the total number of calixpyrrole units in theextractant. ^(g)Calculated from total potassium extracted. ^(h)Based onthe total number of crown ether units in the extractant. ^(i)Notdetermined.

Example 6 Copolymer I can Extract Potassium Chloride

The ability of Copolymers I, II, and III to extract KCl from aqueousmedia was evaluated using conditions analogous to those employed for theKF studies described in Example 5. In this case, after exposing thepolymers to 3.4 M solutions of KCl in D20, FES was again used todetermine the relative amounts of potassium extracted. Copolymer Iproved to be the most effective extractant, displaying an EI value of0.761, which corresponded to a potassium concentration of 12.97±0.08 mMin the organic phase, with the exact quantification being based on thecalibration described above. Copolymers II and III displayed relativelylower EI values, namely 0.507 and 0.081, respectively, values thatcorresponded to potassium concentrations of 8.64 and 1.38±0.08 mM,respectively. The higher overall extraction values for KCl compared toKF is consistent with the relative aqueous solvation energies (ΔG_(h))of chloride and fluoride anions (ΔG_(h)=−340 kJ mol⁻¹ for F⁻ versusΔG_(h)=−465 kJ mol⁻¹ for F⁻). Specifically, the more hydrophobic anion(Cl⁻) was extracted more effectively than its more hydrophilic analogue(F⁻).

Example 7 Copolymer I can Selectively Extract Potassium Ions

Whether potassium salts could be selectively extracted in the presenceof their sodium analogues was examined A 0.5 mL H₂O solution of KCl(134.1 mM) and NaNO₃ (1.47 M) was treated with Copolymer I (in 0.75 mLCH₂Cl₂) and analyzed using FES (using the methods described above inExperiment 5). KCl and NaNO₃ were combined deliberately to form NaCl insitu. The EI of the signal corresponding to potassium (0.734) was overan order of magnitude greater than the signal corresponding to sodium(0.043). These data suggest that Copolymer I extracts potassium chloridemuch more effectively than it does sodium chloride. This finding, whichis in accord with the relative hydration energies of K⁺ and Na⁺(ΔG_(h)=−295 kJ mol⁻¹ for K⁺ and ΔG_(h)=−365 kJ mol⁻¹ for Na⁺), suggeststhat these materials may ultimately enable the selective separation ofpotassium halide salts from complex aqueous mixtures, e.g., in specialtymedical applications.

The compounds and methods of the appended claims are not limited inscope by the specific compounds and methods described herein, which areintended as illustrations of a few aspects of the claims and anycompounds and methods that are functionally equivalent are within thescope of this disclosure. Various modifications of the compounds andmethods in addition to those shown and described herein are intended tofall within the scope of the appended claims. Further, while onlycertain representative compounds, methods, and aspects of thesecompounds and methods are specifically described, other compounds andmethods and combinations of various features of the compounds andmethods are intended to fall within the scope of the appended claims,even if not specifically recited. Thus a combination of steps, elements,components, or constituents may be explicitly mentioned herein; however,all other combinations of steps, elements, components, and constituentsare included, even though not explicitly stated.

The invention claimed is: 1-38. (canceled)
 39. A polymeric compoundcomprising a calix[4]pyrrole unit covalently bound to a polymer backboneselected from the group consisting of polyacryonitrile, polyacrylate,polystyrene, polyester, polyurethane, polyamide, or a co-polymerthereof.
 40. The polymeric compound of claim 39, further comprising acrown ether unit covalently bound to the polymer backbone.
 41. Thepolymeric compound of claim 40, wherein the crown ether unit is abenzo-15-crown-5 ether.
 42. A method of removing an ionic species from asolution comprising adding a polymeric compound comprising acalix[4]pyrrole unit covalently bound to a polymer backbone selectedfrom the group consisting of polyacryonitrile, polyacrylate,polystyrene, polyester, polyurethane, polyamide, or a co-polymer thereofto the solution.
 43. The method of claim 42, wherein the polymericcompound further comprises a crown ether unit covalently bound to thepolymer backbone.
 44. The method of claim 43, wherein the crown etherunit is a benzo-15-crown-5 ether.
 45. A method of treating or preventingan ion imbalance in a subject comprising: selecting a subject having anelevated level of an ion; and administering to the subject a polymericcompound comprising a calix[4]pyrrole unit covalently bound to a polymerbackbone selected from the group consisting of polyacryonitrile,polyacrylate, polystyrene, polyester, polyurethane, polyamide, or aco-polymer thereof.
 46. The method of claim 45, wherein the polymericcompound further comprises a crown ether unit covalently bound to thepolymer backbone.
 47. The method of claim 46, wherein the crown etherunit is a benzo-15-crown-5 ether.